step 10: idle mode

src/arch/x86/lib/instructions.zig

@@ -19,6 +19,9 @@ pub fn cli() void {
 pub fn sti() void {
     asm volatile ("sti");
 }
+pub inline fn hlt() void {
+    asm volatile ("hlt");
+}
 
 pub inline fn int3() void {
     asm volatile ("int3");

src/console.zig

@@ -8,6 +8,10 @@ var input_write_index: u10 = 0;
 var command: [10]u8 = undefined;
 var command_len: usize = 0;
 
+fn sleep_for_2() void {
+    task.usleep(2 * 1000 * 1000) catch unreachable;
+}
+
 fn execute(input: []u8) void {
     const eql = std.mem.eql;
     if (eql(u8, input, "clear")) return vga.clear();
@@ -16,6 +20,7 @@ fn execute(input: []u8) void {
     if (eql(u8, input, "tasks")) return task.format();
     if (eql(u8, input, "tasks")) return task.format_short();
     if (eql(u8, input, "lspci")) return pci.lspci();
+    if (eql(u8, input, "sleep2")) return sleep_for_2();
     if (eql(u8, input, "uptime")) return time.uptime();
     println("{}: command not found", input);
 }

src/main.zig

@@ -26,12 +26,14 @@ export fn kmain(magic: u32, info: *const multiboot.MultibootInfo) noreturn {
     pci.scan();
 
     task.new(@ptrToInt(topbar)) catch unreachable;
-    task.new(@ptrToInt(console.loop)) catch unreachable;
+    // task.new(@ptrToInt(console.loop)) catch unreachable;
 
-    while (true) {
-        task.lock_scheduler();
-        task.schedule();
-    }
+    console.loop();
+    unreachable;
+    // while (true) {
+    //     task.lock_scheduler();
+    //     task.schedule();
+    // }
 }
 
 pub fn panic(a: []const u8, b: ?*builtin.StackTrace) noreturn {

src/task.zig

@@ -1,6 +1,5 @@
 pub usingnamespace @import("index.zig");
 
-var timer_last_count: u64 = 0;
 var boot_task = Task{ .tid = 0, .esp = 0x47, .state = .Running };
 
 const TaskNode = std.TailQueue(*Task).Node;
@@ -17,6 +16,7 @@ var tid_counter: u16 = 1;
 ///ASM
 extern fn switch_tasks(new_esp: u32, old_esp_addr: u32) void;
 
+var timer_last_count: u64 = 0;
 pub fn update_time_used() void {
     const current_count = time.offset_us;
     const elapsed = current_count - timer_last_count;
@@ -114,7 +114,7 @@ pub fn unblock(node: *TaskNode) void {
 pub fn switch_to(chosen: *TaskNode) void {
     assert(chosen.data.state == .ReadyToRun);
 
-    // in case of self preemption
+    // in case of self preemption, shouldn't happen really
     if (current_task.data.state == .Running) {
         current_task.data.state = .ReadyToRun;
         ready_tasks.append(current_task);
@@ -133,21 +133,66 @@ pub fn switch_to(chosen: *TaskNode) void {
     @noInlineCall(switch_tasks, chosen.data.esp, @ptrToInt(old_task_esp_addr));
 }
 
+fn notify_idle() void {
+    const bg = vga.background;
+    const fg = vga.foreground;
+    const cursor = vga.cursor;
+    vga.background = fg;
+    vga.foreground = bg;
+    vga.cursor = 80 - 4;
+    vga.cursor_enabled = false;
+
+    print("IDLE");
+
+    vga.cursor_enabled = true;
+    vga.cursor = cursor;
+    vga.background = bg;
+    vga.foreground = fg;
+}
+
+pub var CPU_idle_time: u64 = 0;
+pub var CPU_idle_start_time: u64 = 0;
 pub fn schedule() void {
     assert(IRQ_disable_counter > 0);
 
     update_time_used();
 
-    // check if somebody wants to run
-    const chosen = ready_tasks.popFirst();
-    if (chosen == null) return unlock_scheduler();
-
+    if (ready_tasks.popFirst()) |t| {
+        // somebody is ready to run
         // std doesn't do this, for developer flexibility maybe?
-    chosen.?.prev = null;
-    chosen.?.next = null;
+        t.prev = null;
+        t.next = null;
+        switch_to(t);
+    } else if (current_task.data.state == .Running) {
+        // single task mode, carry on
+        return unlock_scheduler();
+    } else {
+        // idle mode
+        notify_idle();
 
-    // switch
-    switch_to(chosen.?);
+        // borrow the current task
+        const borrow = current_task;
+
+        CPU_idle_start_time = time.offset_us; //for power management
+
+        while (true) { // idle loop
+            if (ready_tasks.popFirst()) |t| { // found a new task
+                CPU_idle_time += time.offset_us - CPU_idle_start_time; // count time as idle
+                timer_last_count = time.offset_us; // don't count time as used
+                println("went into idle mode for {}usecs", time.offset_us - CPU_idle_start_time);
+
+                if (t == borrow) {
+                    t.data.state = .Running;
+                    return unlock_scheduler(); //no need to ctx_switch we are already running this
+                }
+                return switch_to(t);
+            } else { // no tasks ready, let the timer fire
+                x86.sti(); // enable interrupts to allow the timer to fire
+                x86.hlt(); // halt and wait for the timer to fire
+                x86.cli(); // disable interrupts again to see if there is something to do
+            }
+        }
+    }
 }
 
 var IRQ_disable_counter: usize = 0;
@@ -158,6 +203,7 @@ pub fn lock_scheduler() void {
     }
 }
 pub fn unlock_scheduler() void {
+    if (IRQ_disable_counter == 0) println("error trying to unlock");
     if (constants.SMP == false) {
         IRQ_disable_counter -= 1;
         if (IRQ_disable_counter == 0) x86.sti();

src/vga.zig

@@ -79,7 +79,7 @@ pub fn topbar() void {
         vga.cursor = cursor;
         vga.background = bg;
 
-        task.usleep(60 * 1000) catch unreachable; // 60ms
+        task.usleep(500 * 1000) catch unreachable; // 60ms
     }
 }